The invention relates to a method for marking quartz glass lamps having at least one fusible metal foil which is surrounded by quartz glass, for supplying electric voltage to luminous means arranged in the interior chamber of a lamp vessel. The luminous means is either an incandescent filament of an incandescent lamp or an electrode for producing a discharge arc in a discharge lamp. In particular, it relates to a method for marking halogen lamps, i.e. either incandescent halogen lamps or discharge lamps with a halogen fill. Furthermore, the invention relates to a quartz glass lamp produced using the method.
Various types of methods are known for marking quartz glass lamps, in particular halogen lamps. In particular, lamps of this type are marked or stamped using what is known as the xe2x80x9cpad printingxe2x80x9d method.
However, this method leads to a number of technical problems. For example, the stamping using the xe2x80x9cpad printingxe2x80x9d method is a method which involves contact with the lamp, which may cause damage to the lamp. Furthermore, a dedicated stamping block has to be produced for each lamp identifier, leading to high costs. Therefore, date stamping of the quartz glass lamps which are to be marked is scarcely possible. In addition, changing the block involves standstill times. A further drawback is that the stamping blocks become worn, thus considerably increasing the risk of stamping errors. Furthermore, the known method has the drawback that the stamping ink has to be fired in using separate heating torches. Another drawback is that the stamp may become scratched over the course of time. Finally, a further drawback results from the fact that the pad printing stamp cannot be checked by means of an automated image-processing system, since the fusible metal foil arranged in the background of the marking causes contrast problems.
Therefore, it is an object of the present invention to provide a method according to the preamble of claim 1 which overcomes the described drawbacks of the conventional marking methods for quartz glass lamps.
It is a further object of the present invention to provide a quartz glass lamp produced in this way.
With a method or a quartz glass lamp having the features of the preamble of claim 1 or claim 8, respectively, these objects are achieved by the features of the characterizing part of claim 1 or claim 8, respectively.
Particularly advantageous embodiments are given in the dependent claims.
In a method according to the invention for marking quartz glass lamps, the fusible metal foil is marked through the quartz glass by means of a laser. This ensures that there is no damage to the quartz glass lamps which are to be marked, since it is a contactless marking method. In addition, the marking method according to the invention is significantly less expensive than the known methods, since there is no need for expensive stamping blocks which have the drawbacks referred to above. Furthermore, there is also no further need to fire in the stamping ink. Finally, the marking method according to the invention results in an optimum colour contrast, i.e. a clearly legible identification of the marking throughout the entire service life of the lamp. A further advantage of the method according to the invention is that the identification or marking cannot be removed. Furthermore, date stamping is now possible without problems. Furthermore, the marking method according to the invention enables the marking quality to be monitored by means of automated image-processing systems, since there are no contrast problems.
In a further advantageous embodiment of the method according to the invention, the fusible metal foil is a molybdenum foil. In particular, it is possible to use a doped molybdenum foil.
In a further advantageous embodiment of the method according to the invention, the laser is a Nd:YAG laser. In this case, a wavelength of 1064 nm is advantageously used for the laser marking. Moreover, it is advantageous if the laser is pulsed. This ensures that, firstly, a high-contrast, readily legible identification of the lamp is produced and, secondly, the service life of the lamp is not impaired by the marking operation.
In a further advantageous embodiment of the method according to the invention, in order to increase the marking rate the laser power is increased and/or the pulse frequency of the laser is reduced. In this way, it is possible to achieve very high throughputs when marking quartz glass lamps, which in turn significantly reduces the costs of marking a single quartz glass lamp.
In a further advantageous embodiment of the method according to the invention, to avoid glass cracks in the pinched area, the laser parameters (laser diameter, laser power, pulse frequency, etc.) are optimally adapted to the marking rate.
In a quartz glass lamp according to the invention, the fusible metal foil forms a marking area, the marking of the marking area taking place through the quartz glass by means of a laser. The advantageous result is a quartz glass lamp which on the one hand cannot be damaged by the marking operation and on the other hand can be produced at low cost, since the costs of the marking method are significantly reduced. Moreover, a permanent, high-contrast marking of the quartz glass lamp is ensured.
In an advantageous embodiment of the quartz glass lamp according to the invention, the fusible metal foil is a molybdenum foil. This foil may additionally advantageously be doped.
In an advantageous embodiment of the quartz glass lamp according to the invention, the glass surface of the pinched area is as smooth as possible, in order to ensure good legibility of the marking.
The invention also relates to the use of a Nd:YAG laser for marking quartz glass lamps having at least one fusible molybdenum foil which is surrounded by quartz glass, for supplying electric voltage to luminous means arranged in the interior chamber of a lamp vessel.